3. the state of the atmosphere at a given time and place depends on: amount of cloudstemperature air pressurewind amount of moisture

4. A thick blanket of gases surrounding the Earth composed of AIR (a mixture of gases) Makes conditions on Earth suitable for life

7. Nitrogen (N) 78% Oxygen (O)21% Also, Carbon Dioxide (CO 2 ), H 2 O Vapor, and Argon (Ar) in small amounts

8. Nitrogen Essential to living things Used to grow & repair cells Cannot obtain N 2 from the air-bacteria fix nitrogen in soil for use

9. Oxygen Essential to living things & some non living Combustion Oxidation (rusting) Molecule O 2 or O 3

10. 3 oxygen atoms bonded together O is an atom of Oxygen (O) O 2 is atmospheric Oxygen (O-O) O 3 is ozone (O-O-O)

11. Absorbs 99% of harmful ultraviolet rays from the sun ozone layer is about 10 to 20 km thick thinning is the result of chloroflorocarbons (CFC’s) containing chlorine, fluorine, and carbon

12. Carbon Dioxide CO 2 Essential to life Plants rely for food Animals-waste product Released during combustion Excess may contribute to global warming

13. Water Vapor Water as a gas H 2 0 Invisible Amount varies by time & place Forms clouds during condensation

14. Particles in Air Air in nature is not pure Contains tiny particles of: Dust Smoke Salt

16. Smog Smoke & fog 1 st used to describe air pollution produced by burning coal during the IR in London

17. Houston on a smoggy day (left) and a clear day (right).

18. Pollutants Harmful substances in air, water, or soil Higher concentrations in larger cities Some natural Most by human activity: Burning fossils fuels such as: Coal, Oil, Gas, Diesel –½ from cars & other vehicles –Factories & power plant

19. Natural Sources Salt Spray Plant pollen Forest fires Soil erosion Dust storms Volcanic eruptions

20. Human Activity Burning fossil fuels Photochemical smog: photo- meaning “light” caused by sunlight on chemicals –Nitrogen in the warm air reacts w/burning hydrocarbons –Irritates breathing, harms plants, damages rubber, paint, & plastics

21. Acid Rain Forms when nitrogen oxides & sulfur oxides (produced from burning fossil fuels) combine w/water in the air Can harm trees, pollute ponds & lakes, & kill small organisms (fish, amphibians, insects, & plants)

22. Improving Air Quality Laws & regulations for filters on: –Cars –Smoke stacks Filters called “scrubbers” More fuel efficient vehicles Public transportation